There are three main species of blowfly which initiate strikes on sheep. The Australian sheep blowfly (Lucilia cuprina) accounts for up to 90 percent of single species strikes across Australia, while the Western Australian brown blowfly (Calliphora albifrontalis) is responsible for initiating up to 15 percent of single species strikes. The lesser brown blowfly (Calliphora dubia) is typically involved in combined strikes. Blowfly maggots developing on sheep can cause a reduced wool clip and a general loss of condition, sometimes resulting in the death of the sheep.
Sheep graziers typically adopt a range of control management activities as part of their blowfly control strategy. Such activities include, but are not limited to, adopting the radical Mules operation with optimum tail length, crutching and drenching at strategic times with insecticides, and suitable grazing management.
Organophosphate insecticides have been widely used since the 1950's for the control of sheep strike, in particular diazinon, fenthion ethyl, chlorfenvinphos, dichlofenthion, coumaphos, and more recently propetamphos. These insecticides are commonly referred to as anticholinesterase compounds as they act by blocking the activity of the enzyme cholinesterase, which is required for removing the neurotransmitter acetylcholine from the post-synaptic membrane after the passage of a nerve impulse.
Organophosphate insecticides can be applied to sheep by either dipping or jetting, although some formulations can be applied as a long wool backline treatment.
Protection against blowfly strike is also provided by the use of synthetic pyrethroids. There are currently two synthetic pyrethroid plus diazinon formulations registered for blowfly and lice control. One of these is applied through a manual applicator and the other using an automatic race.
There is growing resistance to the use of organophosphates and synthetic pyrethroids for blowfly strike control. The present invention seeks to overcome at least some of the above mentioned disadvantages.